<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>cricle</title>
    <style type="text/css">
        .leftDiv,.rightDiv{float: left;position: relative;width: 50px;height: 100px;overflow: hidden;}
        .leftInnerDiv,.rightInnerDiv{position:absolute;width: 200%;height: 100%;border:5px solid yellowgreen; border-radius: 50%;box-sizing: border-box  }
        .leftInnerDiv {clip: rect(0px,100px,100px,50px);animation: rotate 2s 2s linear forwards;}
        .rightInnerDiv {left:-100%;clip: rect(0px,50px,100px,0px);animation: rotate 2s 2s linear forwards;}
        @keyframes rotate {
            from{transform: rotate(0deg);}
            to{transform: rotate(180deg);}
        }
    </style>
</head>
<body>
    <div class="outerDiv">
        <div class="leftDiv">
            <div class="leftInnerDiv"></div>
        </div>
        <div class="rightDiv">
            <div class="rightInnerDiv"></div>
        </div>
    </div>
</body>
</html>